Orthotrichum casasianum
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| Orthotrichum casasianum | |
|---|---|
Scientific classification  | |
| Kingdom: | Plantae |
| Division: | Bryophyta |
| Class: | Bryopsida |
| Subclass: | Bryidae |
| Order: | Orthotrichales |
| Family: | Orthotrichaceae |
| Genus: | Orthotrichum |
| Species: | O. casasianum |
| Binomial name | |
| Orthotrichum casasianum F.Lara, Garilleti & Mazimpaka (1999) | |
Orthotrichum casasianum is a species of moss in the family Orthotrichaceae. It is endemic to the Spanish province of Álava, in the Basque Country.[2] It grows in less than 200 trees on the banks of the Bayas river.[3][4] The species is critically endangered, and was added in 2013 to the Basque Catalog of Threatened Species.[5]
Orthotrichum casasianum is a small epiphytic moss forming loose, olive-green cushions up to about 20 mm across, with individual shoots 6–10 mm tall. The leaves are erect and become slightly flexuose (gently zigzag) when dry, measuring 2.0–2.8 mm long by 0.4–0.6 mm wide. They are linear-lanceolate to linear-oblong, with margins recurved (rolled under) for much of their length. Leaf tips are broadly rounded or obtuse, often concave, and typically bear a minute one- or two-celled mucro (tiny hair-like point). Upper leaf cells are thick-walled and either smooth or bear very low papillae (small bumps), whereas basal cells are larger, transparent (hyaline), thin-walled and rectangular.[6]
Reproductive structures occur on autoicous plants (bearing both male and female organs on the same shoot). Sporophytes have short setae (stalks) 0.4–0.6 mm long, carrying emergent urn-shaped capsules up to 2 mm in length. When dry, these capsules are cylindrical-urceolate (barrel-shaped) with eight distinct longitudinal ribs and hemicryptoporous stomata (pores half-hidden in the capsule wall) around the upper half. The double peristome (ring of "teeth" around the mouth) comprises an outer layer of sixteen teeth fused into eight pairs; each tooth shows a reticulate (network-like) pattern of low papillae externally and is almost smooth internally. The inner peristome consists of sixteen smooth, markedly incurved segments. The protective calyptra (cap) is naked, smooth and distinctly folded.[6]